Kingsley Tian, 30, is charged with aggravated assault of a public servant and retaliation, according to Houston police.
Two firefighters in an ambulance were coming back from a call just before 6 p.m. on Monday, stopped at a traffic light in the 3200 block of Wilcrest, when Tian came to a stop next to them, HPD said.
That's when he reportedly pointed a gun at them, police said. No shots were fired.
Officials said the firefighters were able to get a photo of Tian's license plate before he drove away.
When officers went to Tian's residence nearby to arrest him, they located a gun, HPD said.
The retaliation charge was added because Tian made threatening remarks as he was being arrested, according to police.